#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
int main()
{	
	double sum = 0;
	double t = 1.0;
	for (int i = 1; i <= 100; i++)
	{
		sum += t / i;
		t = -t;
	}
	printf("%lf", sum);
	return 0;
}